Felt like I had been shot, or hit
with a bat, and Iíve had both happen before." Thatís how a lance
corporal described an injury he suffered during a live-fire
grenade-assault course in the desert.
While riflemen suppressed targets from squad base-of-fire
positions, another squad maneuvered within hand-grenade range.
After tossing grenades, the Marines ducked behind berms for cover.
After the grenades detonated, the squad resumed suppression. One
corporal picked up his M16, and when he fired, it exploded. His
receiver shattered, and a fragment blew off, cutting a lance
corporal who was behind him, in the neck.
A review of this incident showed that four other M16-A2 rifles
had been similarly damaged during the two-week training. One rifle
had a bullet and cleaning-rod section lodged in the bore, while
the other four were probably fired with sand in their bores. The
mishap rifle had a bullet lodged in its barrel, and since the
shrapnel from this weapon contributed to the injury, it was set
aside for the investigation.
The corporal hadnít had any malfunctions or ammunition
problems, and he hadnít heard an audible pop from his weapon
before the explosion.
An audible pop is a strange noise made when a primer detonates
but fails to ignite all or any of the propellant. The primer has
enough power to kick the projectile out of the case, and if a
small portion of the propellant ignites, it can lodge the
projectile partway down the barrel. To clear the weapon, a Marine
must unload, remove his bolt, and punch out the lodged bullet. If
a Marine fails to clear the projectile and simply performs
immediate action (ejecting the partly spent cartridge and
chambering another round), then fires, the weapon likely will
The ammunition was tested, and nothing unusual was discovered.
If a case had been overloaded or exposed to direct sunlight, the
chamber pressure during firing wouldnít have exceeded 70,000 psi.
The damaged rifles were exposed to pressures nearly three times
the normal amount (fig. 1).
Did the armorers fail to maintain the weapons? No. The unitís
weapons had been inspected on schedule and had gauged within
standard. With everything else ruled out, it became clear these
weapons were destroyed because operators handled them carelessly,
and let sand collect inside their barrels.
The corporal was lying behind a berm with his weapon, while
Marines from another squad threw grenades. When the last grenade
went off, he picked up his rifle, unintentionally scooped up sand
with his muzzle, and fired. The round went off and sent the bullet
down the barrelóplowing sand as it went. The sand wedged between
the bullet and the bore, creating so much friction the bullet
skidded to a stop. The powder behind it, however, continued to
burn, and the chamber pressure rose above 100,000 psi. With the
barrel blocked, the path of least resistance was now through the
The intense heat and extreme pressure forced its way through
the unsupported base of the brass case into the receiver through
the extractor slot (fig. 2). Since the M16ís extractor isnít fully
supported by barrel-locking recesses, the extractor peeled back,
and the bolt carrier and upper receiver split (fig. 3). Gas vented
down through the magazine and out the right side of the rifle
through the ejection port. The left side of the receiver provided
no escape for the gas, and the left side ruptured, blew off, and
hit the lance corporal. The limited technical inspection (LTI)
following the mishap didnít list the lower receiver as damaged;
but often the lower receiver bulges, and the front pivot-pin lugs
are sheared off.
During this training, Marines had to move, shoot and throw
grenades. Rushing from one position to another, repeatedly diving
to the prone, firing and laying rifles in the sand to throw
grenades, presents a number of opportunities for sand to enter a
The mishap board recommended the unit "ensure proper
maintenance is being conducted during live-fire training." Instead
of saying "proper maintenance," they should have said "proper
weapons handling." Since armorers arenít expected to check
headspace and barrel erosion during an assault, and operators
canít clean weapons while moving downrange, the endorsing chain
switched "during" to "before and after." This recommendation is
more practical, but, clearing sand after itís in your weapon is
reactive. Wouldnít it be better to determine how sand collected in
the barrels and find ways to keep it out?
The injured lance corporal and the five destroyed rifles could
have been spared if this potential hazard had been identified and
some simple controls had been implemented to reduce it.
Make sure Marines donít stick their muzzles in the sand, and
donít assume they wonít do it. All it takes is a momentary
distraction. Squad and team leaders are the most likely
candidates, followed by AT4 gunners and gun team members.
Marines have limited experience using both grenades and small
arms on live-fire maneuver ranges. If they use both hands to prep
a grenade while lying in the prone, where is their rifle? Probably
lying in the sand.
Sling and carry weapons muzzle down; present them from the
alert, ready or "indoor-ready," not the tactical carry. If a
Marine scoops a flash-hider full of sand and dirt when he prepares
to rush, where will sand run when he advances with his weapon
Use the issue, shoot-through, plastic muzzle caps to keep sand
and dirt out of weapon barrels. The $2,000 spent to replace five
rifles could have bought 40,000 5-cent muzzle caps.
Training Marines to adjust to their operating environment is
the cheapest option. Injuring one Marine, destroying five rifles,
and leaving five Marines unarmed is too costly.
Operation Under Unusual Conditions (page 81, TM 05538C-10/1A)
Hot, Dry ClimateóDesert
Dust and sand will get into the rifle and
magazines. This will cause malfunctions. Give the inside and
outside areas and functional parts of the rifle a thorough
cleaning every day and after every firing mission.
Donít use too much oil. Corrosion is less likely to form
on metal parts in a dry climate; therefore, lubrication should
be applied to the internal working surfaces and functional parts
only. Use normal amounts of CLP for lubrication. Unload and dry
ammo and inside of magazines daily. Do not lube magazines.
Use bags and caps. The use of overall rifle protection
cover, muzzle cap, and spare magazine protective bags will help
protect the rifle and ammo from sand or dust. Use these items
when the tactical situation permits.
Keep ejection port cover closed. However, as a minimum
effort to keep out sand and dust, keep the bolt and ejection
port cover closed, a magazine installed in the rifle, and a
muzzle cap on the muzzle.
- Clean Daily.
Note: Removal of the muzzle cap before firing is recommended.
Place it in your pocket for future use. However, it is not
dangerous to fire the rifle with the cap installed.
SEE THIS FILE OF
ANOTHER M-16A2 Failure